


Rotten to the CORE

by SoulOfEmerald



Category: Undertale (Video Game)
Genre: Alternate Universe - Zombie Apocalypse, Minor Violence, Multi, Other Additional Tags to Be Added, POV Alternating, Pre-Canon, Survival
Language: English
Status: In-Progress
Published: 2017-01-28
Updated: 2017-01-28
Packaged: 2018-09-20 09:51:26
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,572
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9485864
Author URL: https://archiveofourown.org/users/SoulOfEmerald/pseuds/SoulOfEmerald
Summary: After an experiment goes wrong, the Underground is thrown into a state of chaos as the caverns fill with the undead.  Surviving monsters are trying to survive against the mounting numbers of the infected, while the infected hunt them down for their souls.  In one group, six monsters band together to try and survive like everyone else.Alphys, the brains.Undyne, the muscle.Papyrus, the reason to live.Sans, the mysterious.Toriel, the kind.Mettaton, the fabulous.Together, these six monsters will have to overcome challenge after challenge, both physical and mental.  The question is, who will live, and who will join the undead?





	

They say that if you listen to the mechanical clicks, whirs, and pings of the CORE for long enough, the sounds would blend into an energizing melody.  Every time I entered the CORE, I would always listen for it, but I could never seem to hear it.  But that didn't explain why was dashing through the place at top speed when I was needed at the lab.  Confused, I thought back to a few minutes ago, in hopes of figuring out why.  Instead of one full memory, I could only recall three small segments.

The first segment barely lasted for five seconds.  I was tinkering around my desk, trying to accomplish who-knows-what.  Without the door opening, a voice that wasn't my own echoed throughout the lab.

“ heya alphys. ” Sans greeted.

“O-Oh!  H-Hi Sans!” I quickly replied, my stutter present as usual.

The segment abruptly ended, and the second segment wasn't very helpful either.  Sans and I were in an elevator that would take us from the lab and directly to the CORE.  I couldn't remember when I had it installed, but it was there.  We were both laughing at a pun that I couldn't remember, but I faintly knew that it was something about gears.  That was all.

The third segment was, by far, the most important of the three.  Unlike the cheerful and friendly atmosphere of the previous two segments, this segment boasted one of fear and dread, which hung thick like a fog.  I dashed in the direction that I could only assume held the elevator.  While I couldn't see him, I knew that Sans would be around here somewhere.  Panic pulsed through me from head to tail, and it didn't help when Sans skidded to a stop next to me after turning a corner, terror lacing his ever-smiling face.

“ i think i lost him! ” Sans reported.  “ i’ve got to protect papyrus!  alphys, you go check on the other patients! ”

I didn't argue as he created, leaped through, and closed one of his shortcuts, and I didn’t think to ask who Papyrus was.  With Sans gone, my attention went solely towards finding my way back to the elevator.  That was, until I picked up the sound of charging footsteps.  Without recalling what the thing even was, I dropped all sensible plans of a place to go in favor of fleeing in whatever direction possible.

 

* * *

 

I somehow managed to run faster than before, to the point where my short legs couldn’t carry me any faster.  That thing…whatever it was, could still be chasing me, and my magic was undoubtedly sub-par.  If my memory was right and there really was something to be afraid of, then I didn’t want to be caught.  If I was, then that would mean game over for sure.  I swerved left and right through the mix and match hallways, hoping and praying that I could find the elevator before my stamina gave out.

Within a few minutes however, exhaustion overtook me and I found myself gasping for air while moving at a snail’s pace.  Luckily for me, I never encountered my pursuer.  Somehow, I eventually found my way to the elevator alive.  I gladly stepped inside, pushed the button that would take me to the lab, and flopped on the floor.

I rested there for quite some time before I heard the familiar click and whir of the elevator doors opening.  My muscles were stiff from the sudden burst of exercise, and as I pulled myself back onto my feet, the doors automatically shut themselves.  Sighing, I reopened the doors and stepped inside the lab.

My pedicured claws clicked against the tile floor as I carefully walked to the area that I liked to call the Treatment Center.  I was supposed to check the patients for something, but it’s hard to find a problem when you don’t know what you’re looking for.  The main lab was a short hallway with two floors.  That was where I did all my work.  This part of the lab however, I couldn’t remember using very often.  Rooms led into other rooms, with their purposes unknown to me.  Except for one.  This was where I would treat the monsters that had “Fallen Down”, as the state was referred to.  Lemon Bread, Master Dog, and Mrs. Drake, just to name a few.

When I got to the doorway leading to the treatment room, I was surprised to hear the sounds of motion from inside.  This surprise was quickly replaced by joy, for that meant one of the patients had awoken from their comatose-like state.  Did the treatment really work?  Did I really just save a life?  I stepped into the doorway, hopes increasing steadily, and mentally squealed with delight when I saw some of the monsters walking about.  I had focused on Master Dog when I noticed how aimlessly they were wandering, and how spaced out they looked.  The most noticeable thing however was how they were foaming at the mouth.  I watched Master Dog as he lumbered over to a still unconscious monster and began to growl softly.  What I saw next made my blood run cold.

Master Dog stopped at the monster’s bedside, and with one quick motion, dug his claws into their flesh.  He rooted around for a few seconds before tugging something into the open.  White light flickered faintly from between his claws.  I never saw that object before in my life, but I had learned enough about it to recognize it instantly.

It was their soul.

A monster’s soul couldn’t exist once the monster itself had died, unless the monster in question was a boss monster.  Even then, it could only exist for a few mere seconds before it shattered.  This monster was nowhere near being a boss monster, and I could both see and hear the soul cracking as the monster was quickly dying.  Before it could shatter, Master Dog opened his foaming mouth as wide as he could and devoured the soul in a single bite.

That seemed to act as an invitation for the other conscious monsters to join in.  Within seconds the sounds of tearing and eating filled the room, making me feel like I was about to lose my lunch while they were having theirs.  With my eyes held open by horror, and my feet chained by shock, I helplessly watched as the unconscious monsters were slaughtered and the awake ones lost their minds.

Eventually, only Mrs. Drake was left unconscious.  Her soul had been nibbled on by a crazed Reaper Bird.  Nibbled on, but not fully eaten.  She had lost most of it, but Reaper Bird had ended up leaving the job only two-thirds done.  She twitched.  It was for her first time since arriving here, and probably her last time.  The monitors that I had set up to keep track of her soul and her HP showed that she wasn’t going to ever see her loving family again before she died.  Just before her HP hit zero, she managed to force one word out of her lungs.

“S-S...S...Snowy…”  She sadly muttered.

And that was it.  Her head hit her pillow as the monitors began to blare a loud warning whistle that was meant to alert me if a patient’s HP had ever fallen to less than ten HP.  This alarm hadn’t had the chance to trigger with the others due to how quickly their HP had been lost, and that the life of a dead monster was well out of my claws.

**_Eight HP._ **

I felt horrible for watching her die like this, but what could I do?

**_Five HP._ **

What would I tell her family?

**_Three HP._ **

What would I tell any of their families?

The alarm cut out, like it was set to do when the monster it was monitoring had died.  I bowed my head, and began to say a silent prayer for the unfortunate mother.

“Sn...ow...y…”

My eyes snapped open.  There was no way she was alive.  It was impossible!  Perhaps it was the treatment?  Were they saved by the power of human determination?  I looked back up at her, half expecting to see a pile of dust despite what I heard.

She was slowly clambering to her feet, her eyes holding the same unfocused gaze as the others.  Her face was completely void of emotion, and she stopped talking in favor of quietly moaning and growling.  She managed to hop off her bed, and her beak started to fill with foam as she surveyed the room.  Her gaze quickly found its way to me.  Upon seeing me, her beak started to foam faster, enough to cause little piles of it to form on the ground.  She ruffled her feathers, then let out an ear-piercing shriek that caused me to reflexively grit my teeth, snap my eyelids shut, and cover my head with my arms as I started to take damage.

When it was done, I lowered my arms, ready to protect my hearing if she started screeching again.  When I opened my eyes, the other monsters had their eyes locked on me.  For a minute, there was no sound besides the sound of my breathing and the hum of the giant fans in a far away room.

Suddenly, Master Dog howled aggressively and lunged at me, startling my legs into motion.  A loud uproar was raised as I made my escape, and I knew that every monster in that room that was capable of chasing me was doing so.  I threw random bits of anything I could get my claws on at my pursuers, ranging from sharp metal bits to a bag of popato chisps.  Recalling how well my plan to enter the elevator worked last time (along with the fact that it was the only way out), I set that as my target once more.

Reaper Bird lunged at me with her long neck and only missed me by a hair.  I panicked, and as a instinctual reaction, punched her in the throat as hard as I could.  It should have hindered her, or made her flinch at the very least.  It didn’t.

It made her angry.

I darted into the elevator room as she reeled in her neck for the next lunge.  I smacked the elevator button, and the doors slid open.  I jumped in, and pressed the button for the main lab repeatedly, as if that would speed up the process.  I could hear the other monsters grow nearer and nearer as my hope began to dwindle.  Finally the doors closed, and the elevator jostled a bit as it began to rise.  I smiled, then began to laugh.  I  _ lived! _

A few seconds later, the elevator jostled again.  And again.  The lights flickered and the metal walls screeched as I realised what was happening.  They had Reaper Bird with them.  They seemed to have no sense of self preservation.  All they seemed to have was an instinct to hunt.

Of course they would climb the elevator shaft.

I prepared what little magic I had, which consisted mostly of some basic orange magic.  Orange magic wouldn’t help me in the slightest, but I still had a single normal attack.  As weak as it was, it could still buy me precious seconds.

The elevator pinged.  I was at the main lab.  The two labs were connected, so it only made sense that the ride between the labs would be much shorter than the one connecting the labs to the CORE.  I threw myself out the door, landing in a heap on the tile floor.  I felt stupid for doing so, because it would’ve been a lot easier to simply  _ exit normally. _

As I picked myself back up, a furry white arm appeared from under the elevator.  The elevator shook and raised up as the predatory monsters crawled out from under it.  I screamed as I ran to the nearest exit and fumbled with the motion controls, but my panic was working against me, and my hand motions were too quick for the doors to detect.  The tiles were scratched as the other monsters made it out from the shaft.  I wasn’t going to make it, was I?

Suddenly, a quick flash of blue light blinded me as I felt a hand land on my shoulder.  I began to hyperventilate as the world started to warp and churn around me.  The other monsters seemed to phase through me and slammed into the door, knocking it off it’s hinges.  There was another flash of blue light, and in a moment of utter terror, I tried to throw another punch.  As I did so, I saw my target slide efficiently out of the way with as little movement as possible in a blur of white, blue, and black.  My mind connected the dots.

“S-Sans?” I cried, relief beginning to drown out adrenaline.  I was breathing heavily, and I was only 50% sure I could avoid passing out from it.

“ sheesh alphys, be a bit more careful !”  he said as he placed his hand back in his pocket like usual.  “ what even happened back there? ”

I explained everything to him, from the unnerving memory fragments to the sudden attack from the patients.  He said nothing, taking in everything I had to say.  I was finishing up with him teleporting me away, when I froze.  They broke the door down.  They broke the door.  Reality hit me like a slap in the face as I realized that there was nothing holding the psychopathic monsters back anymore.  I led them to freedom.  Anything they did was my fault.  Naturally, I tacked this knowledge onto the end of my description.

“ alphys, don’t worry about it.  the royal guards will find a way to calm them down. ” he said, knowing how much I believed in Undyne.  “ speaking of calming down, you might want to take a seat, over here- ”  He gestured to a green couch.  Was this where he lived?  “ -and turn on some tv.  there’s a mettaton marathon going on if you want to watch that. ”

Suddenly, a loud, heavily accented voice boomed out from another room.  “SANS?  DID YOU INVITE A GUEST?”

“ sorry for not telling you bro, but this is a bit of an emergency. ”

Sans had a  _ brother _ ?  Despite me not knowing that, it seemed to faintly ring a bell.  Perhaps he told me a while back, and I’ve just forgotten?  Probably.

“NO NEED TO APOLOGIZE!  I ALWAYS MAKE EXTRA SPAGHETTI, JUST IN CASE!”

I noticed the clock at the bottom of their VCR.  5:47 PM.  No wonder he was cooking, it was near supper time!  Before I could even speak, an alarm went off.  Naturally, I darted up a staircase that was located on the left side of the room and prepared my magic, knowing what happened the last time an alarm went off.

“ relax alphys, it’s just a fire alarm. ”  Sans comforted, before entering the room which I could only assume was the kitchen.  Embarrassed, I made my way back down the stairs and onto the couch.  Taking Sans’s suggestion from earlier, I found the remote on the coffee table and turned on the TV.  After a bit of channel flipping, I found my favorite channel, which showed anime of all sorts.  I smiled, and told myself everything would be okay.

  
I never was that good at lying, especially to myself.

**Author's Note:**

> I like how I said I had a schedule in place, then proceeded to immediately deviate from said schedule.
> 
> This actually is technically my oldest fic on here. I was already writing this chapter before I even started to write the other stories. I got stuck at one point though and never got around to working on it. That was, until today. I'm sorry if this fic doesn't update often. It takes longer to write it than you'd think. Plus, this will probably be my longest fic once it's done, so that also might effect things. 
> 
> Anyway, I'm rambling way too much. I hope you enjoyed, and I'll see you next time!
> 
>  
> 
> p.s. Yes, the title is a double pun.


End file.
